Packaged microelectronic devices with pressure release elements and methods for manufacturing and using such packaged microelectronic devices

ABSTRACT

Packaged microelectronic devices, interconnecting units for packaged microelectronic devices, and methods and apparatuses for packaging microelectronic devices with pressure release elements. In one aspect of the invention, a packaged microelectronic device includes a microelectronic die, an interconnecting unit coupled to the die, and a protective casing over the die. The interconnecting unit can have a substrate with a first side and a second side to which the die is attached, a plurality of contact elements operatively coupled to corresponding bond-pads on the die, and a plurality of ball-pads on the first side of the substrate electrically coupled to the contact elements. The protective casing can have at least a first cover encapsulating the die on the first side of the substrate. The packaged microelectronic device can also include a pressure relief element through at least a portion of the first cover and/or the substrate. The pressure relief element can have an opening to an external environment and a passageway to an internal location within the packaged microelectronic device. In operation, the pressure relief element releases gases or other forms of moisture entrapped by the casing and/or the substrate during high temperature processing of the packaged microelectronic device.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.09/645,640, now U.S. Pat. No. 6,979,595, filed on Aug. 24, 2000.

TECHNICAL FIELD

The present invention relates to packaging microelectronic deviceshaving a microelectronic die including an integrated circuit. Moreparticularly, several aspects of the invention are related to releasingpressure within packaged microelectronic devices during high temperatureprocesses, such as reflow processing and burn-in testing.

BACKGROUND

Microelectronic devices, such as memory devices and microprocessors,typically include a microelectronic die encased in a protectivecovering. The die can include memory cells, processor circuits,interconnecting circuitry and/or other functional features. The die alsotypically includes an array of very small bond-pads electrically coupledto the functional features. When the die is packaged, the bond-pads arecoupled to leads, solder ball-pads or other types of terminals foroperatively coupling the microelectronic dies to buses, circuits and/orother microelectronic devices.

Several different techniques have been developed for packagingmicroelectronic dies. The dies, for example, can be incorporated intoindividual packages, mounted with other components in hybrid or multiplechip modules, or connected directly to a printed circuit board or othertypes of substrates. When a die is incorporated into an individualpackage, the bond-pads on the die are typically coupled to a lead frame,and the die is covered or otherwise sealed from the environment. Whenthe die is attached directly to a printed circuit board or another typeof substrate, the bond-pads on the die are typically coupled tocorresponding contact elements on the substrate using wire-bond lines,ball grid arrays and other techniques. The dies that are mounteddirectly to the substrates are generally Chip Scale Package devices(CSP) or Flip Chip Bare Die devices (Flip-Chip).

CSP and Flip-Chip devices generally have one or more protective casingsthat encapsulate the dies and any exposed contact elements, bond-pads orwire-bond lines. The protective casings should shield the die and theother components on the substrate from environmental factors (e.g.,moisture), electrical interference, and mechanical shocks. Theprotective casings are accordingly robust elements that protect thesensitive components of a microelectronic device. The protective casingsare generally composed of plastics, ceramics, or thermosettingmaterials.

One conventional technique for fabricating the protective casingsinvolves placing the die in a cavity of a mold, and then injecting athermosetting material into the cavity. The thermosetting material flowsover the die on one side of the substrate until it fills the cavity, andthen the thermosetting material is cured so that it hardens into asuitable protective casing for protecting the die. According toconventional practices, the protective casing should not have any voidsover the die because contaminants from the molding process orenvironmental factors outside of the mold could damage the die. Thethermosetting material, moreover, should not cover a ball-pad array onthe substrate or damage any electrical connections between the die andthe substrate. Therefore, according to conventional practices, thethermosetting material should be molded in a manner that avoids (a)producing voids in the protective casing, (b) covering certain portionsof the substrate with the thermosetting material, and (c) displacing orotherwise damaging any wire-bond lines or solder joints between the dieand the substrate.

One drawback of packaging microelectronic devices is that duringhigh-temperature processing cracks or voids can form in the protectivecasing, or the protective casing can delaminate from the substrate. Suchcracking or delamination, for example, may occur during a solder reflowprocedure in which the packaged microelectronic devices are quicklyheated to reflow solder balls and/or or solder paste pads. This problemis particularly noticeable in procedures that quickly heat the packageddevices to an elevated temperature. When the casing of a packagedmicroelectronic device cracks or delaminates from the substrate, thedevice is often rejected because such cracks or voids can expose verydelicate components (e.g., bond-pads or wire-bond lines) to externalenvironmental factors. It will be appreciated that such cracking of thecasing results in extremely expensive losses because it occurs at theend of the fabrication process after a significant amount of money hasbeen expended to manufacture each packaged microelectronic device.Therefore, it would be desirable to develop an apparatus and method forreducing or completely preventing the casing from cracking ordelaminating from the substrate during high temperature processing.

SUMMARY

The present invention is directed toward packaged microelectronicdevices and methods for making and using such packaged microelectronicdevices. In one aspect of the invention, a packaged microelectronicdevice includes a microelectronic die, an interconnecting unit coupledto the die, and a protective casing over the die. The microelectronicdie, for example, may have an integrated circuit and a bond-pad arrayhaving a plurality of bond-pads operatively coupled to the integratedcircuit. The interconnecting unit has a substrate with a first side anda second side to which the die is attached, a plurality of contactelements operatively coupled to corresponding bond-pads on the die, anda plurality of ball-pads on the first side of the substrate. Theinterconnecting unit can also include a plurality of conductive elementsextending from selected contact elements to corresponding ball-pads toelectrically couple the contact elements to the ball-pads. Theprotective casing can have at least a first cover encapsulating the dieon the first side of the substrate.

The packaged microelectronic device can also include a pressure reliefelement through at least a portion of the first cover and/or thesubstrate. The pressure relief element can have an opening to anexternal environment and a passageway to an internal location orinterior point within the packaged microelectronic device. The pressurerelief element, for example, can be a hole or opening through thesubstrate to an adhesive strip on the bottom side of the die. In anotherembodiment, the pressure relief element is a hole through the firstcover to either the substrate or the microelectronic die. In stillanother embodiment, the pressure relief element is a depression thatextends only part way through the cover or the substrate such that thepassageway forms a thin section of the first cover or the substrate. Inoperation, the pressure relief element releases gases or other forms ofmoisture entrapped by the casing and/or the substrate during hightemperature processing of the packaged microelectronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top cut-away isometric view illustrating a portion of amicroelectronic device in accordance with an embodiment of theinvention.

FIG. 2A is a top isometric view of the microelectronic device of FIG. 1.

FIG. 2B is a front cross-sectional view of the microelectronic device ofFIG. 2A.

FIG. 3 is a front cross-sectional view of a microelectronic device inaccordance with another embodiment of the invention.

FIG. 4A is a bottom isometric view and

FIG. 4B is a front cross-sectional view of a microelectronic device inaccordance with another embodiment of the invention.

FIGS. 5A and 5B are front cross-sectional views of a microelectronicdevice in accordance with another embodiment of the invention.

FIGS. 6A and 6B are front cross-sectional views of a microelectronicdevice in accordance with still another embodiment of the invention.

FIG. 7 is a side cross-sectional view of a microelectronic device and amold assembly used to form a protective casing with pressure reliefelements in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The following disclosure is directed toward packaged microelectronicdevices, interconnecting units for packaged microelectronic devices, andmethods for manufacturing and using packaged microelectronic devices.Several embodiments of the invention are described with reference tomemory devices, but the methods and apparatuses are also applicable tomicroprocessors and other types of devices. One skilled in the art willaccordingly understand that the present invention may have additionalembodiments, or that the invention may be practiced without several ofthe details described below.

FIG. 1 is a top cut-away isometric view of a microelectronic device 10in accordance with one embodiment of the invention. The microelectronicdevice 10 can include a substrate 20 and a microelectronic die 40attached to the substrate 20 by an adhesive strip 60. The followingdescription is directed toward encapsulating a microelectronic die on aflexible substrate, but it is expected that several embodiments of themethods and apparatuses in accordance with the present invention may bepracticed to encapsulate a large variety of electrical and/ornon-electrical articles. Therefore, the following description withrespect to encapsulating the microelectronic die 20 shown in FIGS. 1–7Bis for purpose of illustration only, and it is not intended to limit thescope of the invention.

The embodiment of the substrate 20 shown in FIG. 1 can have a first end21, a second end 22 opposite the first end 21, a first surface 23, and asecond surface 24 opposite the first surface 23. The substrate 20 canalso include an elongated slot 25 between the first and second surfaces23 and 24 that extends lengthwise along a medial portion of thesubstrate 20. Additionally, an aperture 26 through the substrate 20 canbe located at a secondary gate location generally proximate to thesecond end 22 of the substrate 20. The substrate 20 is one component ofan interconnecting unit that provides an array of ball-pads for couplingvery small bond-pads on the microelectronic die 40 to voltage sources,signal sources, and/or other input/output sources. In the embodimentshown in FIG. 1, the substrate 20 includes an array of ball-pads 27, anarray of contact elements 28 proximate to the slot 25, and a trace 29 oranother type of conductive line between each ball-pad 27 and acorresponding contact element 28. The substrate 20 can be a flexiblematerial or a substantially rigid material, and the traces 29 can beconductive lines that are printed on the substrate in a manner similarto printed circuit boards.

The embodiment of the microelectronic die 40 shown in FIG. 1 includes afront side 41, a plurality of bond-pads 42 on the front side 41, and anintegrated circuit 44 (shown schematically). The front side 41 of thedie 40 is attached to the second surface 24 of the substrate 20 by anadhesive strip 60. The bond-pads 42 are coupled to the integratedcircuit 44, and the bond-pads 42 are also arranged in an array along thefront side 41 of the microelectronic die 40 so that the bond-pads 42 arealigned with or otherwise accessible through the slot 25 in thesubstrate 20. A plurality of wire-bond lines 50 or other types ofconnectors couple the bond-pads 42 on the die 40 to correspondingcontact elements 28 on the substrate 20. As such, the substrate 20distributes the very small bond-pads 42 to the larger array of ball-pads27. The die 40 projects away from the second surface 24 of the substrate20 such that a backside 45 of the die 40 is spaced apart from the secondsurface 24 of the substrate 20.

The microelectronic device 10 can further include a protective casinghaving a first cover 70 a over the die 40 and a second cover 70 b overthe slot 25. The first and second covers 70 a and 70 b can be formedfrom a thermosetting material, ceramics, or other suitable materials.The first and second protective covers 70 a and 70 b can be molded asexplained in U.S. patent application Ser. No. 09/255,554, which isherein incorporated by reference.

The embodiment of the microelectronic device 10 shown in FIG. 1 alsoincludes a plurality of pressure relief elements 80 that are configuredto release a gas entrapped in the microelectronic device 10. Thesubstrate 20 and/or the adhesive strip 60 can absorb moisture, and thefirst and second covers 70 a and 70 b can entrap this moisture in thearea around the die 40. When the microelectronic device 10 is quicklyheated in a solder reflow process or another high-temperature procedure,the entrapped moisture expands and creates a pressure gradient in themicroelectronic device 10. The pressure relief elements 80 provide apath through which the expanding gas can escape without cracking thecovers 70 a or 70 b, delamninating the substrate 20 and/or the covers 70a or 70 b, or otherwise damaging the microelectronic device 10.

FIG. 2A is a top isometric view and FIG. 2B is a front cross-sectionalview that illustrate various embodiments of the pressure relief elements80 in further detail. Referring to FIG. 2A, the pressure relief elements80 can be a series of passageways completely through the substrate 20 atan area outside of the ball-pads 27. The pressure relief elements 80 canbe of elongated channels (shown on one side of the cover 70 b), or thepressure relief elements 80 can be holes (shown on the other side of thesecond cover 70 b). The pressure relief elements 80 can also be shorterelongated channels or slots that fit between the ball-pads 27 and thetraces 29 (shown in broken lines). In a typical application, thepressure relief elements 80 will be either elongated channels on bothsides of the second cover 70 b, or a series of holes on both sides ofthe second cover 70 b (as shown in FIG. 1). Referring to FIG. 2B, thepressure relief elements 80 include a passageway 82 having a first enddefined by an opening 84 at an external location and a second end at aninterior point 86 of the microelectronic device 10. In the particularembodiment shown in FIG. 2B, the opening 84 is at the first surface 23of the substrate 20 and the interior point 86 is at the second surface24 of the substrate 20.

The pressure relief elements 80 of the embodiment shown in FIG. 2B arealso positioned over the adhesive strip 60 to expose a portion of theadhesive 60 to the external environment. The location of the pressurerelief elements 80 is generally selected to provide a passageway tointernal locations within the substrate where moisture is likely to beentrapped. Thus, as explained in more detail below, the pressure reliefelements 80 can be configured to allow moisture to escape from thesubstrate 20, the adhesive 60, the covers 70 a and 70 b, and/or anycombination of these components.

The pressure relief elements 80 shown in FIGS. 1–2B can be formed byetching or laser cutting the substrate 20 before attaching the adhesive60 to the second surface 24 of the substrate 20. The pressure reliefelements 80, for example, can be etched by masking the substrate 20 witha photo resist and etching through the substrate 20 with a suitableetchant. Similarly, a laser can cut through the substrate 20 usingtechniques that are known in the art. The pressure relief elements 80can also be formed by mechanically drilling (e.g., gang drilling),punching, stamping, or molding the holes or slots in the substrate 20.

The microelectronic device 10 is particularly well suited for use inhigh temperature post-encapsulation processes, such as solder reflowprocessing and burn-in testing. When the microelectronic device 10 issubject to a process that rapidly increases the temperature, theexpansion of the moisture entrapped in the substrate 20, the adhesive60, and/or the first and second covers 70 a and 70 b generates apressure gradient in the internal region of the microelectronic device10. The adhesive tape 60, for example, is particularly subject toabsorbing moisture, and thus a pressure gradient typically forms in theregion of the adhesive 60 during high temperature processing. Thepressure relief elements 80 allow the moisture in the tape 60 and theother components of the device 10 to diffuse out of the device 10 beforelarge pressure gradients are created in the substrate 20 or the firstand second covers 70 a and 70 b. The pressure relief elements 80 areaccordingly expected to inhibit or completely prevent cracking ordelaminating of the covers 70 a and 70 b during high temperatureprocessing.

FIG. 3 is a front cross-sectional view of a microelectronic device 10 ain accordance with another embodiment of the invention. In thisembodiment, the microelectronic device la includes a substrate 20, a die40 attached to the substrate 20 by an adhesive 60, and the first andsecond covers 70 a and 70 b. The microelectronic device 10 a can alsoinclude a plurality of pressure relief elements 80 that are defined bypassageways 82 extending through the substrate 20. Unlike themicroelectronic device 10 in which the passageways 82 extend to theadhesive 60, the pressure relief elements 80 of the microelectronicdevice 10 are defined by passageways 82 that extend from the firstsurface 23 of the substrate 20 to the second surface 24 of the substrate20 at a location over the first cover 70 a and spaced apart from theadhesive 60. The microelectronic device 10 a accordingly providespressure relief elements 80 for allowing moisture to diffuse out of thesubstrate 20 and the first cover 70 a during high temperatureprocessing. In another embodiment, the pressure relief elements 80 shownin FIGS. 2B and 3 are combined in a single microelectronic device havinga first plurality of pressure relief elements 80 that expose theadhesive 60 to the external environment (FIG. 2A) and a second pluralityof pressure relief elements 80 expose the interior of the first cover 70a to an external environment (FIG. 3).

FIG. 4A is a bottom isometric view and FIG. 4B is a frontcross-sectional view of a microelectronic device 10 c in accordance withanother embodiment of the invention. Referring to FIG. 4A, themicroelectronic device 10 c has a plurality of pressure relief elements80 extending through the first cover 70 a. Referring to FIG. 4B, thepressure relief elements 80 can be a series of passageways 82 extendingthrough a top portion of the first cover 70 a. Each passageway 82 canhave an opening 84 exposed to external environment and an interior point86 at the backside 45 of the die 40. In operation, the pressure reliefelements 80 shown in FIG. 4B allow moisture to escape from the firstcover 70 a during high temperature processing.

FIGS. 5A and 5B are front cross-sectional views of a microelectronicdevice 500 in accordance with another embodiment of the invention.Referring to FIG. 5A, the microelectronic device 500 includes asubstrate 520 having a first surface 523 and a second surface 524. Thedie 40 is attached to the second surface 524 of the substrate 520, thefirst cover 70 a encases the die 40, and the second cover 70 b encasesthe bond-pads 42 and the wire-bond lines 50 at the first surface 523 ofthe substrate 520. Several components of the microelectronic device 500can be similar to the components of the microelectronic device 10 shownin FIG. 2B, and thus like reference numbers refer to like components inFIGS. 2B, 5A and 5B. The substrate 520, for example, can also have aslot 25, a plurality of contact elements 28 adjacent to the slot 25, aplurality of ball-pads 27 spaced apart from the contact elements 28, anda plurality of conductive elements electrically coupling selectedcontact elements to corresponding ball-pads 27.

The microelectronic device 500 can also include a plurality of pressurerelief elements 580 through a portion of the substrate 520. In theembodiment illustrated in FIG. 5A, the pressure relief elements 580 aredepressions 582 that have an opening 584 at the first surface 523 on thesubstrate 520 and an interior point 586 proximate to the second surface524 of the substrate 520. The depressions 582 do not extend completelythrough the substrate 520 such that the interior point 586 of thepressure relief elements 580 is at an intermediate depth in thesubstrate 520. The pressure relief elements 580 can be superimposed overthe adhesive strips 60 (shown in FIG. 5A), or the pressure relief 580can be located over the first cover 70 a in a manner similar to thepressure relief elements 80 shown in FIG. 3.

FIG. 5B illustrates the operation of the pressure relief elements 580 inthe microelectronic device 500. As the microelectronic device 500 isheated during a high temperature process, the expanding moisture in theadhesive 60, the substrate 520, and/or the covers 70 a and 70 b canrupture the thin section of the substrate 520 at the interior point 586of a passageway 582 to form a via 588 through which the expanding gascan escape. The pressure relief elements 580 accordingly act as pressurerelief valves that rupture to prevent the pressure gradient frombecoming so large that it cracks or otherwise delaminates the first orsecond covers 70 a or 70 b. The thickness “t” of the thin section of thesubstrate 520 between the interior point 586 and the second surface 524can accordingly be selected to rupture and form the via 588 at apressure that is less than the failure pressure of the first and secondcovers 70 a and 70 b.

The pressure relief elements 580 can also be fabricated by lasercutting, etching, drilling, stamping, embossing, or molding thesubstrate 520. A laser, for example, can have a residence time that doesnot penetrate through the substrate 520 but rather only forms thedepression 582 without passing through the second surface 524. Suitablelaser and etching techniques that can form a controlled depression areknown in the art.

FIGS. 6A and 6B are front cross-sectional views of a microelectronicdevice 600 in accordance with yet another embodiment of the invention.Several components of the microelectronic device 600 can be similar tothe components of the microelectronic device 10 shown in FIG. 2B, andthus like reference numbers refer to like parts in FIGS. 2B, 6A and 6B.The microelectronic device 600 can also include a plurality of pressurerelief elements 680 through a portion of the first cover 70 a. Thepressure relief elements 680, for example, can be a plurality ofdepressions 682 having an opening 684 and an interior point 686. Theopening 684 is exposed to external environment, and the interior point686 is at an intermediate depth in the first cover 70 a. Referring toFIG. 6B, the thin section of the first cover 70 a between the interiorpoint 686 and the backside 45 of the die 40 can rupture during a hightemperature process to relieve pressure in the first cover 70 a. Theleft-most pressure relief element 680 a in FIG. 6B, for example,illustrates a ruptured pressure relief element 680 that forms a via 688through which high pressure gas can escape from the microelectronicdevice 600. As set forth above, the thickness t of the first cover 70 abetween the back side 45 of the die 40 and the interior point 686 of thepressure relief element 680 can be selected to rupture at apredetermined pressure that is less than the failure pressure of thethicker portion of the cover 70 a. As such, the pressure relief elements680 can act as pressure relief valves that are positioned atpredetermined failure sites to relieve pressure within themicroelectronic device 600 before the first cover 70 a or the secondcover 70 b cracks or has another type of catastrophic failure.

FIG. 7 is a side cross-sectional view of a mold assembly and a methodfor forming the first cover 70 a for the microelectronic device 600shown in FIGS. 6A and 6B. The mold assembly can include a first moldsection 200 and a second mold section 300. The first mold section 200has a bearing surface 220 and a wire-side cavity 224, and the secondmold section 300 has a bearing surface 320, a die-side cavity 324, and aplurality of posts 329 in the die-side cavity 324. The wire-side cavity224 is configured to form the second cover 70 b over the slot 25 of thesubstrate 20, and the die-side cavity 324 is configured to form thefirst cover 70 a over the die 40. The second mold section 300 can alsoinclude a gate 326 and an injection chamber 328 through which a flow Fof mold compound (e.g., thermosetting material) is injected into thedie-side cavity 324.

During the molding process, the substrate 20 is positioned between thefirst and second mold sections 200 and 300 to align the die 40 with thedie-side cavity 324 and to align the slot 25 with the wire-side cavity224. The bearing surface 320 of the second mold section 300 pressesagainst the second surface 24 of the substrate 20, and the bearingsurface 220 of the first mold section 200 can press against the firstsurface 23 of the substrate 20. The bearing surface 220 of the firstmold section 200 can engage the first surface 23 of the substrate 20 byinjecting a mold compound into the die-side cavity 324, as explained inU.S. patent application Ser. No. 09/255,554. The flow of mold compound Finitially passes through gate 326 of the second mold section 300 andcontinues into the die-side cavity 324 to create a first flow A₁ of moldcompound heading in a first direction toward the second end 22 of thesubstrate 20. The first flow A₁ of mold compound passes through theaperture 26 in the substrate 20 to generate a second flow B₁ of moldcompound that flows through the wire-side cavity 224 of the first moldsection 200. The second flow B₁ of mold compound fills the slot 25 ofthe substrate 20 and flows in a second direction until it reaches aterminal end 227 of the wire-side cavity 224. When the mold compoundsufficiently fills the die-side cavity 324 and the wire-side cavity 224,the post 329 in the die-side cavity 324 form the pressure reliefelements 680 in the first cover 70 a shown in FIGS. 6A and 6B.Similarly, to form the pressure relief elements 80 in the first cover 70a shown in FIG. 4B, the posts 329 can be lengthened so that they engagethe back side 45 of the substrate 40 when the bearing surface 320 of thesecond mold section 300 engages the second surface 24 of the substrate20.

From the foregoing it will be appreciated that specific embodiments ofthe invention have been disclosed for purposes of enablement andillustration, but that various modifications may be made withoutdeviating from the spirit and scope of the invention. For example,certain embodiments of the pressure relief elements 80 shown in FIGS.2A–3 or the pressure relief elements 580 shown in FIGS. 5A and 5B canalso relieve pressures caused by mechanical stresses as a result of thedifferent coefficients of thermal expansion for the different componentsof the microelectronic device 10. The substrate 20 generally has adifferent coefficient of thermal expansion than the molding compound ofthe first and second covers 70 a and 70 b. The microelectronic device 10generally has a low level of internal mechanical stress at roomtemperature because the first and second covers 70 a and 70 b shrinkafter cooling from the molding process. During high temperatureprocessing, however, the microelectronic substrate 10 can have highinternal mechanical stresses because the first and second covers 70 aand 70 b can expand much more than the substrate 20. The elongatedpressure relief elements 80 shown on the one side of the cover 70 b inFIG. 2A are expected to reduce the internal mechanical stresses causedby different thermal expansion/contraction characteristics of thedifferent components in the microelectronic device 10 because theelongated pressure relief elements 80 act as expansion joints. Thus, theterm pressure relief element can include structures that provide a paththrough which gas can escape from the microelectronic device, thatrelieve internal mechanical stresses caused by different thermalexpansion/contraction characteristics, and/or that control or otherwisedissipate other internal stresses in microelectronic devices.Accordingly, the invention is not limited except by the appended claims.

1. A packaged microelectronic device, comprising: a microelectronic diehaving an integrated circuit and a bond-pad array having a plurality ofbond-pads operatively coupled to the integrated circuit; aninterconnecting unit having a substrate with a first side and a secondside to which the die is attached, a plurality of contact elementsoperatively coupled to corresponding bond-pads on the die, a pluralityof ball-pads on the first side, and a plurality of conductive elementsextending from selected contact elements to corresponding ball-pads; aprotective casing having at least a first cover encapsulating the die onthe second side of the substrate; and a plurality of pressure reliefelements through at least a portion of the first cover, the individualpressure relief elements having an opening to an external environmentand a passageway to an internal location.
 2. A packaged microelectronicdevice, comprising: a microelectronic die having an integrated circuitand a bond-pad array having a plurality of bond-pads operatively coupledto the integrated circuit; an interconnecting unit having a substratewith a first side and a second side to which the die is attached, aplurality of contact elements operatively coupled to correspondingbond-pads on the die, a plurality of ball-pads on the first side, and aplurality of conductive elements extending from selected contactelements to corresponding ball-pads; a protective casing having at leasta first cover encapsulating the die on the second side of the substrate;and a plurality of pressure relief elements through at least a portionof the first cover and/or the substrate, the individual pressure reliefelements having an opening to an external environment and a passagewayto an internal location, wherein each pressure relief element is adepression in the first cover and/or the substrate that does not passcompletely through the first cover and/or the substrate such that theopening is at an external side of the first cover and/or the substrateand the internal location is at an intermediate depth within the firstcover and/or the substrate, the first cover and/or the substrate havinga thickness between the internal location and the second side that isconfigured to rupture at a predetermined pressure.
 3. The device ofclaim 2 wherein: the microelectronic die is attached to the second sideof the substrate by an adhesive; and the depressions are over theadhesive.
 4. The device of claim 1 wherein the individual pressurerelief elements are holes completely through the first cover such thatthe internal location is at a backside of the die.
 5. The device ofclaim 1 wherein the individual pressure relief elements are depressionsin the first cover that do not pass completely through the first coversuch that the internal location is at an intermediate depth within thefirst cover, the first cover having a thickness between the internallocation and a backside of the die that is configured to rupture at apredetermined pressure.
 6. A packaged microelectronic device,comprising: a microelectronic die having an integrated circuit and abond-pad array having a plurality of bond-pads operatively coupled tothe integrated circuit; an interconnecting unit having a substrate witha first side and a second side to which the die is attached, a pluralityof contact elements operatively coupled to corresponding bond-pads onthe die, a plurality of ball-pads on the first side, and a plurality ofconductive elements extending from selected contact elements tocorresponding ball-pads; a protective casing having at least a firstcover encapsulating the die on the second side of the substrate; and aplurality of pressure relief elements through at least a portion of thefirst cover, the individual pressure relief elements being configured torelease a gas entrapped by the casing.
 7. A packaged microelectronicdevice, comprising: a microelectronic die having an integrated circuitand a bond-pad array having a plurality of bond-pads operatively coupledto the integrated circuit; an interconnecting unit having a substratewith a first side and a second side to which the die is attached, aplurality of contact elements operatively coupled to correspondingbond-pads on the die, a plurality of ball-pads on the first side, and aplurality of conductive elements extending from selected contactelements to corresponding ball-pads; a protective casing having at leasta first cover encapsulating the die on the second side of the substrate;and a plurality of pressure relief elements through at least a portionof the first cover and/or the substrate, the individual pressure reliefelements being configured to release a gas entrapped by the casingand/or the substrate, wherein each pressure relief element is adepression in the first cover and/or the substrate that does not passcompletely through the first cover and/or the substrate such that theopening is at an external side of the first cover and/or the substrateand the internal location is at an intermediate depth within the firstcover and/or the substrate, the first cover and/or the substrate havinga thickness between the internal location and the second side that isconfigured to rupture at a predetermined pressure.
 8. The device ofclaim 7 wherein: the microelectronic die is attached to the second sideof the substrate by an adhesive; and the depressions are over theadhesive.
 9. The device of claim 6 wherein the individual pressurerelief elements are holes completely through the first cover such thatthe internal location is at a backside of the die.
 10. The device ofclaim 6 wherein the individual pressure relief elements are depressionsin the first cover that do not pass completely through the first coversuch that the internal location is at an intermediate depth within thefirst cover, the first cover having a thickness between the internallocation and a backside of the die that is configured to rupture at apredetermined pressure.
 11. A packaged microelectronic device,comprising: an interconnecting unit having a substrate with a first sideand a second side, a slot defining an open region between the first andsecond sides, a plurality of contact elements on the first side andadjacent to the slot, a plurality of ball-pads on the first side, and aplurality of conductive elements on the first side extending fromselected contact elements to corresponding ball-pads; a microelectronicdie having an integrated circuit and a plurality of bond-padsoperatively coupled to the integrated circuit, the die being attached tothe second side of the substrate, and the bond-pads being aligned withthe slot; a plurality of wire-bond lines in the slot extending betweenselected bond-pads on the die and corresponding contact elements on thesubstrate; a protective casing having a first cover encapsulating thedie on the second side of the substrate and a second cover encapsulatingthe bond-pads, the wire-bond lines and the contact elements; and apressure relief element through at least a portion of the first coverand/or the substrate, the pressure relief element being configured torelease a gas entrapped by the casing and/or the substrate.
 12. Thedevice of claim 11 wherein the pressure relief element is a depressionin the substrate that does not pass completely through the substratesuch that the opening is at the first side of the substrate and theinternal location is at an intermediate depth within the substrate, thesubstrate having a thickness between the internal location and thesecond side that is configured to rupture at a predetermined pressure.13. The device of claim 12 wherein: the microelectronic die is attachedto the second side of the substrate by an adhesive; and the depressionis over the adhesive.
 14. The device of claim 11 wherein the pressurerelief element is a depression in the first cover that does not passcompletely through the first cover such that the internal location is atan intermediate depth within the first cover, the first cover having athickness between the internal location and a backside of the die thatis configured to rupture at a predetermined pressure.
 15. Aninterconnecting unit for use in packaging a microelectronic device,comprising: a substrate with a first side and a second side, the secondside being configured to receive the die; an adhesive attached to thesecond side of the substrate; a contact array with a plurality ofcontact elements on the first side and/or the second side; a ball-padarray with a plurality of ball-pads on the first side; a plurality ofconductive elements extending from selected contact elements tocorresponding ball-pads; and a pressure relief element through at leasta portion of the substrate positioned at a location apart from thecontact elements and over the adhesive, the pressure relief elementhaving an opening at the first side of the substrate and an internallocation at least proximate to the second side of the substrate suchthat the adhesive is exposed to the external environment.
 16. The unitof claim 15 wherein the pressure relief element is a hole completelythrough the substrate such that the opening is at the first side of thesubstrate and the internal location is at the second side of thesubstrate.
 17. The unit of claim 15 wherein the pressure relief elementis an elongated channel completely through the substrate such that theopening is at the first side of the substrate and the internal locationis at the second side of the substrate.
 18. An interconnecting unit foruse in packaging a microelectronic device, comprising: a substrate witha first side and a second side, the second side being configured toreceive the die; a contact array with a plurality of contact elements onthe first side and/or the second side; a ball-pad array with a pluralityof ball-pads on the first side; a plurality of conductive elementsextending from selected contact elements to corresponding ball-pads; anda pressure relief element through at least a portion of the substratepositioned at a location apart from the contact elements, the pressurerelief element having an opening at the first side of the substrate andan internal location at least proximate to the second side of thesubstrate, wherein the pressure relief element is a depression in thesubstrate that does not pass completely through the substrate such thatthe opening is at the first side of the substrate and the internallocation is at an intermediate depth within the substrate, the substratehaving a thickness between the internal location and the second sideconfigured to rupture at a predetermined pressure.
 19. The unit of claim18 wherein: the interconnecting unit further comprises an adhesiveattached to the second side of the substrate; and the depression is overthe adhesive.